Transcript Proteins Chapter 7

Health Benefits of Protein
Protein- Positive Image
• Conjures up images of vitality and strength
Protein- Positive Image
• Has not been accused of being
fattening
Protein- Positive Image
• Has not been accused of causing tooth decay
or Increasing the risk of heart disease
Protein is a "big seller”
• Protein drinks, pills, and powders fill
the shelves of health food stores.
Chapter Learning Outcomes
1. Identify the basic structural unit of proteins.
2. Distinguish between essential and nonessential
amino acids.
3. Explain the basic steps of protein synthesis and
digestion.
4. Discuss conditions that contribute to positive
nitrogen balance, negative nitrogen balance, and
protein balance.
Chapter Learning Outcomes (continued)
6. Identify food sources of protein and foods that
provide high and low quality proteins.
7. Plan meals and snacks that reduce animal protein
intake.
8. Discuss the pros and cons of vegetarian diets.
9. Describe how protein-energy malnutrition (PEM)
can affect the body.
Quiz Yourself
True or False

1. Animal foods such as meat and eggs are almost 100% protein.
T F
2. Foods made from processed soybeans can be sources of high
quality protein. T F
3. An adult body builder should consume about five times more
protein than a healthy adult who is not a body builder. T F
4. Registered dietitians generally recommend that vegetarians
take amino acids supplements to increase their protein
intake. T F
5. People can nourish their hair by using shampoo that contains
protein. T F
How Did You Do?

1. False Animal foods such as meat and eggs contain
some protein, lipids, and lots of water.
2. True Foods made from processed soybeans can be
sources of high quality protein.
3. False An adult body builder does not need to
consume about five times more protein than a
healthy adult who is not a body builder.
4. False Registered dietitians do not generally
recommend that vegetarians take amino acids
supplements to increase their protein intake.
5. False Hair is composed of protein, not living tissue.
Therefore, it cannot be nourished.
What Are Proteins?
• Complex organic molecules
– Chemically similar to lipids and
carbohydrates
• Composed of carbon, hydrogen, oxygen, and nitrogen
• The human body contains ~100,000 different
proteins.
Why We Need Protein
• Growth and repair of tissues
• As a secondary source of energy
Why We Need Protein
• Energy source—provides 4 kcal/gram
• Support & movement—bone matrix, cartilage,
muscle (skeletal, heart, peristalsis, etc...)
• Biochemical reactions—all enzymes are
proteins
• Regulators—some hormones are proteins
(insulin)
• Oxygen carriers—hemoglobin and myoglobin
are proteins
Why We Need Protein
• Antibodies are proteins—attack foreign
proteins and microorganisms to prevent
infections and poisoning
• Buffering—blood proteins maintain blood pH
which keeps the environment favorable for
chemical reactions
• Water balance/osmoregulation—albumin in
the Blood
• Neurotransmitters—nerve signaling
Amino Acids
Essential Amino Acids
1. Phenylalanine
2. valine
3. threonine
4. Tryptophan
5. isoleucine
6. Methionine
7. histidine
8. lysine
9. leucine
Non Essential Amino Acids
1. Glycine
2. Alanine
3. Cysteine
4. Serine
5. Aspartate
6. Asparagine
7. Glutamate
8. Glutamine
9. Proline
10. Tyrosine
Protein Sparing
• When energy intake is adequate, body protein
will be spared for protein-specific functions
(building tissues, etc…). So carbohydrate and
fat spares protein.
• When energy intake is limiting, even if protein
intake is “adequate”, some body protein will
be burned for energy.
Protein Sparing
• Protein losses can be minimized during weight
reduction by consuming >0.8 g protein/kg
each day. However, this does not need to be
taken to the extreme such as 2.0 gm
protein/kg.
Does the Protein Requirement Differ
According to the Protein Quality of the
Diet?
• Protein quality is determined by two things:
– Digestibility—refers to the amount of the
protein that is digested and absorbed
– Biologic value—refers to the amino acid
make-up of the protein
Protein Quality: Digestibility
• What happens to the nutritional value of a
protein if it is not well-digested?
• Growth and maintenance are slowed because
the body manufactures fewer proteins
Protein
intake=
60 g amino
acids
70% of
protein
digested
(60 x .7
42 g amino
acids
available for
absorption
Classifying Amino Acids
Essential Amino Acids
• Cannot be made by the body, so must
be supplied in the diet
• 9 of the 20 amino acids
Nonessential Amino Acids
• Can be made by the body
• 11 of the 20 amino acids
Protein Quality
• What happens if the pattern of essential
amino acids in the diet don’t match the body’s
required pattern of essential amino acids?
• Can your body build what it needs to? NO!
Quality of Protein in Foods
• The highest quality food proteins are those that
are both very digestible and have an essential
amino acid pattern closely matching the amino
acid requirements of the body.
• The food proteins of highest quality are:
– Egg—contains the highest quality protein of all foods
– Milk
– Meat, fish
Limiting Amino Acid
• The limiting amino acid in a food is the
essential amino acid that is present in the
smallest amount relative to the essential
amino acid requirement of the body.
Limiting Amino Acids in Foods
Food
Grains, nuts,
seeds
Legumes
(includes soy and
peanuts)
Corn
Green Leafy
Vegetable
Most Limiting AA High Levels
Lysine, threonine Methionine
Methionine
Lysine, threonine
Lysine,
tryptophan
Methionine
Methionine
Protein and Effect in the Body
A diet containing lots of animal protein may
cause:
– high cholesterol heart disease
– more bone mineral loss osteoporosis
– Why? Protein or other components?
Soy protein substituted for animal protein
– lowers blood cholesterol, may prevent
– osteoporosis—why? Protein or other
components?
How Does it Work
• Addition—Adding more protein, at some
point, you’ll have enough of the limiting
essential amino acid
• Supplementation—A better quality protein
can fill in the missing essential amino acids
• Complementation—What one protein lacks
the other has
Overcoming Protein Quality
Shortages
• How would you improve the protein quality of
a diet?
– Eat more protein—addition
– Eat higher quality protein—supplementation
– Combine proteins of lower quality that
complement each other—complementation
Improving Protein Quality
Addition
Large amounts of rice, bread or
pasta are eaten in many
countries
Supplementation Milk + cereal, meat in vegetable
stew, egg in stir-fried vegetables
Complementation peanut butter sandwich,
tortillas/beans, rice & tofu, grains
and leafy vegetables
You need to know the nine essential
amino acids
• A way to remember the essential amino acids
• "These Ten Valuable Amino-acids Have Long
Preserved Life In Man."
OR
• PV. TTM HILL
The Essential and Nonessential Amino Acids
Insert table 7.1
A quick review
• The building blocks of proteins are referred to
as:
(a)amino acids (b) enzymes (c )hormones
(d)Antibodies
A body function that is not associated with
protein is (a) blood clotting (b)cholesterol
synthesis (c) formation of antibodies
(d) tissue growth and maintenance
A quick review
• List the functions of protein
• Name the three groups of atoms that make up
a protein.
• How many types of amino acids are needed to
make human protein?
• How many of these amino acids are essential?
Proteins in Foods
• Nearly all foods contain some protein, but no
natural food is 100% protein.
• Animal foods typically have more protein than
plant foods.
– Seeds, tree nuts, and legumes supply more protein
than fruit or the edible leaves, roots, flowers, and
stems of vegetables.
Protein Contents of Some Commonly Eaten Foods
• Insert Table 7.2
What Are Legumes?
• Legumes
– Plants that produce
pods with a single
row of seeds
Examples:
Soybeans, peas,
peanuts, lentils, and
beans
Insert figure 7.3
Protein Quality
• High-quality protein or “Complete protein”
– Protein that contains all 9 essential amino acids in
amounts that support growth- meat, poultry, egg, milk
– Most animal products and products made with
processed soy
– Note: Well digested and absorbed in the body
• Low-quality protein
– Protein that lacks or has inadequate amounts of one or
more of the essential amino acids
– Most plant foods (except processed soy)
and gelatin
Note: Body does not digest as efficiently.
What Happens to Protein in Your Body?
• How Your Body Synthesizes Proteins
– Cells assemble the 20 amino acids in specific
sequences according to information provided by
DNA.
– Amino acids are connected by peptide bonds.
– Peptides
• Chains of fewer than 15 amino acids
– Polypeptides
• Proteins made of > 50 amino acids
What Is a Protein?
• Each distinctive bead in
the illustration represents
a different amino
acid.
• The “hook” that
connects the “beads”
represents a peptide
bond.
Insert figure 7.4
Peptide Bond
• Insert figure 7.5
Protein Synthesis
• Insert figure 7.6
A Protein Takes Shape
• Insert figure 7.7
Sickle Cell Anemia
• If the DNA code is faulty, the wrong amino acid may be inserted into a
protein. For example, sickle cell disease that affects red blood cells
Insert figure 7.4
Protein Denaturation
Denaturation
• Altering a protein’s natural shape and function by exposing it
to conditions such as heat, alcohol, acid, and physical
agitation
– Heat denatures the protein in raw eggs.
– Acidic lemon juice “curdles” the protein in milk.
– Hydrochloric acid denatures food proteins in the
stomach, making them easy to digest.
– Physical agitation includes whipping protein-rich foods
(e.g., beaten egg whites).
• Once a protein has been denatured, it cannot return
to its original shape.
Denaturation
Insert Figure 7.9
Protein Turnover
• Protein turnover
– Breaking down old or unneeded proteins into
amino acids and recycling the amino acids
• Amino acid “pool”
– Amino acids that have not been incorporated into
proteins
• Endogenous amino acids
– Those available from the amino acid pool
• Exogenous proteins
– Those from dietary sources
Transamination and Deamination
Transamination
– Transfer of nitrogen-containing group from an
unneeded amino acid to a carbon skeleton, forming
an amino acid
Deamination
– Removal of nitrogen-containing group from an
unneeded amino acid
Example of Transamination and Deamination
Insert Figure 7.10
The Liver and
Deamination
Ammonia (NH3) is
converted to urea
that the kidneys
excrete in urine.
Insert Figure 7.11
What happens if you eat too
protein?
The body DOES NOT store the extra amino acids
in muscles or other tissues.
The extra amino acids undergoes deamination.
The cells convert the carbon skeletons into
glucose or fat, or metabloizes them for energy.
Nitrogen Balance
Nitrogen balance (or equilibrium)
Balancing nitrogen intake with nitrogen losses
Positive nitrogen balance
Body retains more nitrogen than it loses
Negative nitrogen balance
Body loses more nitrogen than it retains
insert Figure 7.12
Positive Nitrogen Balance
Occurs during growth, pregnancy, recovery from illness, and as a
result of certain hormones and resistance exercise
Insert Figure 7.12
Nitrogen Equilibrium
Occurs when healthy adults meet protein and energy needs
Insert Figure 7.12
Negative Nitrogen Balance
Occurs with  protein intake, kidney disease, blood loss, bed rest, fever,
injuries, burns, or  thyroid hormone or cortisol
How Much Protein Do You Need?
• Daily protein needs of healthy adults:
– RDA = 0.8 g/kg body wt
• Protein needs increase during periods of
growth, pregnancy, lactation, and recovery
from illness or injury.
Determining Protein Needs
•
Using the RDA formula of 0.8 g of protein/kg of body wt,
what is the RDA for protein for a person weighing 165 lbs?
1) Convert weight in lbs to weight in kg
(165  2.2 = 75 kg)
2) Multiply kg of body wt by 0.8
75 X 0.8 = 60
Therefore, a person weighing 165 lbs will meet his/her RDA for
protein by consuming 60 g of protein per day
Protein Digestion
• Protein digestion begins in the stomach.
– Hydrochloric acid denatures proteins
– Pepsin, an enzyme, digests proteins into smaller
polypeptides.
• Polypeptides enter the small intestine
– The enzymes trypsin and chymotrypsin break down
polypeptides into shorter peptides and individual amino
acids.
Protein Absorption
• Absorption occurs in the small intestine
– Absorptive cells release enzymes that digest most
small peptides into individual amino acids.
– Individual amino acids and some di- and
tripeptides enter absorptive cells, where they are
completely digested to amino acids.
After Absorption…
• Amino acids enter portal vein and travel to the
liver
– Liver keeps some amino acids for its own use and
releases others into general circulation.
• Most proteins are digested and amino acids
absorbed
– Very little protein is eliminated in feces.
What Is A Food Allergy?
• Allergy
– Inflammatory response resulting when body’s
immune system reacts inappropriately to a
substance that is typically harmless
• Allergen — the offending substance
– Most food allergens are proteins that escape
digestion and are absorbed as whole proteins.
Common Signs of Food Allergies
Signs occur within a few minutes or
couple of hours and typically include:
–
–
–
–
–
–
–
Hives (red raised bumps on skin)
Swollen or itchy lips
Skin flushing
Scaly skin rash (eczema)
Difficulty swallowing
Wheezing and difficult breathing
Abdominal pain, vomiting, and diarrhea
Common Food Allergens
Protein-rich foods
- Cow’s milk
- Eggs
- Peanuts
- Wheat
- Soybeans
- Fish and shellfish
Nonproteins
- Food dyes
- Sulfites added to:
•
•
•
•
Wine
Fruits
Vegetables
Shellfish
Who Develops Food Allergies?
• People with family history of food or
environmental allergies
• ~ 4% of children 5 to 17 yrs
• Most outgrow by age 5 yrs
– Allergies to nuts, seafood, and
wheat are typically not outgrown
• ~ 2% of adults
Gluten and Celiac Disease
• Gliadin
– Protein found in gluten of wheat, buckwheat,
barley, and rye
– Triggers inflammatory response in small intestine
– Condition called celiac disease
• Symptoms include
– Chronic diarrhea, weight loss, poor growth in
children
• Treatment
– Avoid gluten-containing foods
•
•
•
•
•
Other Sources of Glutensrces of
gluten supplements
Medications and vitamin/mineral
Glues and pastes
Communication wafers
Grain derived alcohol such as beer
Contamination of safe grains with unsafe grains
– Bulk grains at food stores
– Toasters
– Airborne flour dust
• Eating out can be tricky
– Growing number of Gluten-free Restaurants
• “Beyond the Grain” in Des Moines
Treatment of Food Allergies
• Avoid offending foods
• Read food labels to check for allergens
• Food Allergen Labeling and Consumer
Protection Act requires manufacturers to
identify allergenic ingredients on product
labels.
• Educate teachers and other adults of
allergic children’s need to avoid certain
foods
Treating Severe Allergic Reactions
Insert photo of
girl using epi
Pen from page 200
Emergency
treatment for
anaphylaxis (a
severe allergic
reaction) may
involve injecting a
special
medication.
What Is PKU?
Phenylketonuria (PKU)
– Genetic disorder
– Affects ~ 1/15,000 infants
– Caused by lack of enzyme that
converts the amino acid
phenylalanine to another
compound
– If undiagnosed, infant will
develop mental retardation by
first birthday.
Insert photo of phenyl
warning from page 201
Low Phenylalanine Diet
Infancy
Phenylalanine-free formula and low-phenylalanine
foods
Childhood and adult years
Allowed: fruits, vegetables, and special lowphenylalanine foods
Avoided: nuts, milk and milk products, eggs, meats,
and foods and beverages containing aspartame (e.g.,
Nutrasweet or Equal)
Questions
• Share some of the things you understand
about protein.
Question
• What information is fuzzy at this time?
Protein Consumption Patterns
Insert Figure 7.14
MyPyramid Plan:
Recommendations for Protein Intake
• Choose lean or low-fat meat and poultry
– Lean cuts of beef include:
• Round steaks, top round, loin, top sirloin, chuck and arm
roasts
– Lean pork cuts include:
• Loin, tenderloin, and center loin
• Choose “extra lean” ground beef
– At least 90% lean
• Trim visible fat from meats
Understanding
Nutritional Labeling
• Nutrition Facts panel only
provides grams of protein
• Panel does not provide
information concerning
protein quality
– Judge protein quality by
reviewing items in the
ingredient list
Figure 7.15
Eating Well for Less
- Substitute eggs, milk, cheese, and yogurt for meat,
fish, or poultry.
- Make meals that contain less animal proteins and
more plant proteins.
- Extend cereal proteins with eggs and milk (e.g.,
pancakes, waffles, crepes, or cereal with milk).
- Include more legumes in meals (e.g., chili, bean
soups, and stews) while reducing meat content.
Combining Complementary Proteins
Complementary combinations
- Mixing certain plant foods to provide all essential
amino acids without adding animal proteins
Amino acids often low or limiting in plant proteins:
tryptophan, threonine, lysine, and
methionine
Limiting Amino Acids in Foods
Food
Most limiting
AA
High Levels
Grains,nuts, seeds
Lysine, Threonine
Methionine
Legumes (includes soybean Methionine
and peanuts)
Peanuts
Lysine, Threonine,
Methionine
Corn
Lysine, Tryptophan
Green leafy vegetables
Methionine
Lysine, Threonine
Methionine
Complementary Dishes
Insert photo of girl
making BPJ from page
207
Peanut Butter (legume) on
Bread (grain)
Insert
couscous
photo from
page 209
Couscous (grain) with
Chickpeas (legume)
Complementary Protein Dishes
• Insert Table 7.3
Vegetarianism
Vegetarians- People who eat plant-based diets
Types of Vegetarians
• Lactovegetarian
• Consumes milk and milk products
• Ovovegetarian
• Consumes eggs
• Lactoovovegetarian
• Consumes eggs and milk and milk products
• Vegan
• Consumes only plant foods
Is Vegetarianism a Healthy Lifestyle?
Pros
• Compared to
nonvegetarians, vegetarians
tend to:
– Weigh less
– Have less heart disease (eat
less saturated fat and
cholesterol)
– Often exercise more,
meditate for relaxation, and
avoid tobacco and alcohol
Cons
• If diets are poorly planned,
vegetarians may lack:
–
–
–
–
–
Kilocalories
High-quality protein
Omega-3 fatty acids
Vitamins B-12 and D
Zinc, iron, and calcium
Vegetarian Children and Teens
Children
• May be difficult to consume adequate protein and energy,
because plant foods tend to be filling
– Growth rates of vegan children need close monitoring.
Teens
Pro: Can be healthy diet because more fruits and
vegetables are consumed
Con: May be at risk of anorexia nervosa, an eating
disorder
Vegetarian Women
Pregnancy
• May need vitamin B-12 supplements
– Infant could be deficient in B-12
Breastfeeding
• Breastmilk may be deficient in vitamin B-12
– Infant may develop severe developmental delays if fed
breast milk that lacks vitamin B-12
Meatless Menu Planning Ideas
• Insert Table 7.4
Protein Adequacy
Excessive Protein Intake
– May  risk of heart disease and cancers of the
colon/rectum, prostate, pancreas, and breast
What about High-Protein Weight-Loss Diets?
– Diets decrease feelings of hunger and increase sense of
fullness.
– More info about safety of high-protein weight loss diets
in Chapter 10
Protein Deficiency
Uncommon in the U.S.
– May occur in:
• elderly or low-income people
• persons with alcoholism, anorexia nervosa, or
intestinal tract disorders
Kwashiorkor and Marasmus
Protein-energy malnutrition (PEM)
– Results from chronic lack of food or poor food choices
Two types of PEM:
– Kwahsiorkor
• Adequate energy intake but intake of high-quality
protein is low
» Edema
– Marasmus
• Starvation—extreme weight loss
Marasmic
Kwashiorkor
Characterized by
edema in the
abdomen, lower
legs, and feet
Insert figure 7.17
Severe ProteinEnergy
Malnutrition
Insert figure 7.18
Chapter 7 Highlight
Building a Bulkier Body
How to increase muscle mass?
• Resistance training is the only safe and
reliable way.
• Dietitians generally do not recommend
eating large amounts of protein-rich foods.
How Resistance Training Builds Bigger
Muscles
• During training, muscle proteins break
down.
– Synthesis occurs during recovery and
lasts ~ 24 to 48 hrs.
• Muscles grow larger if adequate energy and
protein are available (positive nitrogen
balance).
Proteins: General Advice for Athletes
• Since carbohydrates spare proteins, eat a snack
before or after exercise that includes adequate
carbohydrate and protein.
• Protein supplements are not needed for healthy
persons.
– If supplements are used, avoid those that contain a
single amino acid.
• Avoid high-protein diets, especially ones high in
red meats.
Be able to: List the primary functions of
proteins in the body
Short Time Plain Cook = CHEF
Structural, Transport, Pigment, Contractile
C-ontractile
H-ormones
E-nzymes
F-luid balance